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Home > Help Needed / General Tech Chat > Differing compression ratio calcs

Steve220

257 Posts
Member #: 11017
Senior Member

Shropshire

17th Jul, 2019 at 11:04:09am

Hi all,

Rather than sift through the ever numerous online calculators, I thought i'd ask on here. My engine is on its way back today, however the builders reckon it will be a 9.4:1 compression ratio. Here's the spec

1310cc (+40)
MED cast pistons 10cc dish (usually sit lower in the block?)
24cc head chamber
BK450 gasket

I roughly worked this out to be 8.8:1?

Edited by Steve220 on 17th Jul, 2019.


Turbo Phil

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4633 Posts
Member #: 20
My sister is so fit I won't show anyone her picture

Lake District

17th Jul, 2019 at 12:28:50pm

Assuming the Omegas are in an unskimmed block, they should sit around 0.040” down the bore.
With that in mind:
V+C/C

V=327.5
C=41.8
So your compression ratio would be 8.83-1

Phil.

WWW.TURBO-MINI.COM


Steve220

257 Posts
Member #: 11017
Senior Member

Shropshire

17th Jul, 2019 at 12:33:45pm




On 17th Jul, 2019 Turbo Phil said:
Assuming the Omegas are in an unskimmed block, they should sit around 0.040” down the bore.
With that in mind:
V+C/C

V=327.5
C=41.8
So your compression ratio would be 8.83-1

Phil.


Hi Phil, that's what i'd roughly worked out, however i don't know how much rob walker took off on the first build, and the current builder have 'only levelled it'. I'll get them to measure the piston/deck height before i leave.

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